Our objective is to study the DNA damage and repair in genes and other regions within the genome. We also use more traditional techniques to study DNA repair in the average, overall genome. Findings (reviewed in Bohr VA et al., Laboratory Investigation 61, 143, 1989), have indicated that active genes are preferentially repaired in mammalian cells and that determinations of DNA repair in specific genes are important for correlations to biological endpoints and risk assessments. Whereas our earlier studies were limited to UV as a damaging agent, we have now developed techniques to study DNA damage and repair after certain carcinogens and cancer chemotherapeutics. We are studying the DNA repair of genes in some human, cancer prone DNA repair deficient syndromes and in various human and rodent mutant cell lines, some of which are transfected with repair genes. We are also investigating the role of DNA repair in multidrug resistance.